Transmission of pictures by electricity



N09. 1, 1927. 1,647,765 H. D. ARNOLD TRANSMISSION OF PICTURES BY ELECTRICITY I Filed May1 1924 2 Sheets-Sheet 1 hrekfnr. Ham/a A Amo/d H. D. ARNOLD TRANSMISSION OF PICTURES BY ELECTRICITY Filed May 1 1924 \r 2 Sheets-Sheet Nov. 1, 1927. 1,647,765

Patented Nov. 1, 1927.

UNITED STATES PATENT OFFICE.

COMPANY, INCORI ORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TRANSMISSION OF PICTURES BY ELECTRICITY.

1 Application filed May 14,

This invention relates to the transmission of pictures by electricity and more particularly to a system adapted for use in a telephone plant.

It was well known prior to this invention that pictures couldbe transmitted from one place and reproduced at another by the use of electricity. At the sending station electric current is produced having characteristicscorresponding to the tone values of elemental areas of the picture to be sent. These characteristics are transmitted to the reproducing station, where corresponding elemental areas of a record blank are operated upon to reproduce the picture. Various arrangements of this sort have been proposed from time to time, but so far as applicant is aware, no commercially successful system has been previously developed.

An object of the present invention is to transmit pictures commercially. Another object is to transmit pictures by the use of equipment which readily fits into the existing telephone plant.

In one embodiment of the invention current from a photoelectric cell is amplified and used to modulate a voice frequency carrier wave in accordance with the varying tone values of a picture, The modulated carrier waveafter transmission over an ordinary telephone circuit is amplified and demodulated by means of threeelectrode electron discharge devices. The demodulated current is used to actuate a light valve to reproduce the picture. Picture drums at the sending and reproducing stations are ro-,

tated in synchronism and moved axially with respect to light sources by phonic wheels whose speed is controlled over one leg of a. composite telegraph circuit. The starting and stopping of the drums is controlled ovcrthe other leg. The complete system is, therefore, operative over a single telephone line The novel features which are considered characteristic of this invention are set forth with particularity in the appended claims. The system incorporating this invention, both as to its organization and method of operation together with other objects and advantages thereof, will be further ex-- plained in the following description having reference to the accompanying drawing, consisting of the following figures:

Fig. 1 shows schematically the apparatus 1924. Serial No. 713,245.

at the sending station and its connection to the transmissioncircuit.

Fig. 2 shows schematically the apparatus located at the reproducing station and likewiste its connection to the transmission circui HAROLD D. ARNOLD, OF MAPLEWOOD, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC Fig. 3 shows diagrammatically an arrangement for moving the drums axially while they are being rotated.

' A complete system is illustrated by plaoing Figs. 1 and 2 side by side from left to right, respectively. 3

Referring now to the system thus illustrated, a sending drum 5. is driven by a phonic wheel 6 by means of, a shaft 7 shown diagrammatically by dotted lines. The coupling between the drum 5..and the phonic wheel 6 is through a friction clutch 8. The phonic wheel 6 is itself driven by tuning fork .SF in'well known manner. A distributor SD having ten segments and a contact ring 9 is provided. A brush 10 mounted on a shaft 7 connects the segments successively to the ring 9, as the phonic 'yvheel 6 revolves. Alternate segments are connected together to form two groups, one of which is connected to the positive terminal of battery 11 and the other to the negative ter minal of battery 12. The other terminals of these batteries are connected to ground. The contact ring 9 is connected by means of conductor 13 to one leg of a composite telegraph set 14, using one conductor of telephone circuit L.

At the reproducing terminal (Fig. 2), the corresponding leg of composite set 15is connected through line relay 16 to ground. A reproducing drum 17 is driven by a phonic wheel 18 through shaft 19, shown diagrammatically by dotted lines. The coupling between the drum 17 and the phonic wheel 18 is through a friction clutch 20 The phonic wheel 18 is driven by a tuning fork RF in well-known manner. tion" of the fork RF is controlled within limits by means of resistance 22 in a manner The speed of vibra-' hereinafter to be described. A: distributor tat-es impulses of current alternatively positive and negative are transmitted to the reproducing terminal to cause the vibration of the armature 25 of line relay 16. The armature vibrates between two contacts 26 and 27. A negative impulse arriving over the line moves the armature against contact 26, where it will remain until a positive impulse arrives when it moves over into engagement with contact 27. A leak'relay 28 is connected with the line relay 16, as shown, with its terminal 29 connected to the contact 27 of line relay 16 through the resistance 30 and its terminal 31 connected to the contact 26 of line relay 16 through resistance 32.

The common terminal of relay 28 is con nected to the negative terminal of battery 4 and to ground. Tts cont-act 33 is connected to the contact 27 above the'resistance 30, while its contact 34 is connectedto the contact 26 above the resistance 32. The current passing through relay 28 from battery 4, contact 26 and resistance 32 will hold the armature in engagement with contact .33,

' where it will remain until the armature 25 connected together, each group of contacts being connected to a terminal of the control relay 36, while the connecting ring 23 is connected" to the armature 35 of leak relay 28. The armature 31 of control relay 36 is con nected to one terminal or" resistance 22, while contact 38 of control relay 36 is connected to the other terminal. When the armature 37 is in engagement with contact 38, resistance 22 is shortcircuitcd, with the result that the rate of vibration of tuning fork RF is increased to speed up the phonic wheel 18. The eflective speed of tuning fork RF is such that the phonic wheel 18 rotates slightly slower than phonic wheel 6 at the sending terminal. With the resistance 22 shortc"rcuited the reverse is true and phonic wheel 18 rotates slightly faster than phonic wheel 6.

If we assume that for any reason the phonic wheel 18 is lagging behind the phonic wheel 6 at the sending station and that if whenthis occurs a positive impulse arrives over the line wire the operation of the synchronizing system will be as follows:

A positive impulse passing through the line relay'16 will cause the armature 25 to move into engagement with contact 27, closing the circuit from battery 4, the armature 25, contact 27, resistance 30 and right hand winding to relay 28, causing the armature 35 of leak relay 28 to move into engagement .with contact 34. Until the armature 35,

memes however, pulls away from the contact 33 a pulse will be sentthrough control relay .36 over a circuit which may be traced from a positive terminal of battery 4, armature 25,

contact 27, conductor 39, contact 33015 leak' relay 28, armature 35, conductor 41, conduct-.

cuiting the resistance 22 and speeding up the tuning fork RF. This increased speed will continue until .the brush carrier 24 is in advance of the brush carrier 10 at the sending station. When a reversal of current occurs in the line relay 16, the armature 25 moves outof engagement with contact 27 and into engagement with contact 26. The armature 35 of leak relay 28 will again cause a pulse of current to be sent from the battery 4 but as at this time the brush is in advance over the corresponding brush at the sending station the pulse will pass by means of the brush through one ofthe other groups of connecting segments and over the conductor, 43,.

through left hand winding toli control relay 36, causing the armature of this relay to move over into engagement with its idle contact, thereby again connecting resistance 22 in series with the driving "magnet of tuning fork RF and causing phonic wheel 18 to 'run more slowly. Thus, the two phonic wheels 6 and 18 are held in substantial synchronism, the accuracy attained being de: pendent upon the number of segments in the receiving distributor RD. The number of segments at the sending distributor SD must be half that at the receiving distributor RD.

When the motor 18 is lagging behindJzhe motor 6, the connections are such that the resistance 22 is shunted a greater part of the time, whereas when the motor 18 is leading the'resistanc'e/22 is included in circuit the greater part of the time.

The drum 5 is normally prevented from rotating by armature 44 of relay 45, which,

when the relay 45 is 'deenergized, engage.

with a stop on the drum '5. Likewise drum 17 is prevented from rotating by armature 46 when relay 47 is deenergized. The ener-' gizing circuitfor relays 45 and '47 extends from ground at relay 45 through the winding-oi relay 455, battery 48, switch 49, the upper leg of compositesets 14 and 1 5 and the winding of relay 47 to ground. By closing switch 49, both drums 5 and 7 are released substantially simultaneously. Any difi erence in the response of the relaysdue to thelength of line between the sending an'dreproducing stations can be compensated for by the relative location of the stops '0 the two drums.

ture in an opaque shield 54. On the surface battery 55 to flow through the photoelectric 57 and resistance 58.

.from the modulator PM is lmpressed upon the telephone line L in. amplified form by of the drum 5 the transparency of the picture to be transmitted is secured and the light passing through this transparency of the picture causes 'a varying current from the cell and to be impressed upon the input circuit 51 of amplifier PCA. The output circuit of amplifier PCA is connected to an electron discharge modulator'PM by means of potentiometer 56. An electrondischarge oscillator PO supplies a carrier wave having a frequency within the voice range, which is also impressed upon the input circuit of modulator PM through transformer The output. current means of sending amplifier SMA.

At the reproducing station-the picture modulated carrier wave from the oscillator PO received from the telephone" line L is amplified by amplifier RA and impressed upon the reproducing demodulator RPD.

' The movable wires of light valve are connected in the output circuit of demodulator RPD in series with battery 59. The aperture between the movable wires of light valve 60 controls the amount of light from a source 61, which afiects a sensitive record blank secured to reproducing drum 17. The light frhm source 61 is focusedjfirst upon the movable wires of the light valve- .60 by lens 62 and then upon. the surface of drum 17 by lens 63. The area exposed, is further defined by an aperture in opaque shield 64.

The oscillator PO includes a three-electrode-electron discharge device, having its input circuit coupled to the output circuit transformer 65. Its frequency is determined by the tuned circuit consisting of the left hand Winding of transfo'rmer 65 and condenser 66 connected in series with the feed-back portion of the output circuit with high resistance 67. .The output wave for transmission purposes is transmitted throughpotentiometer 68.

he amplifiers PCA, SMA, and RA each include three-electrode-electron discharge devices and rare so designed. as. to properly transmit and amplify ,thewaves impressed thereon. Similarly, the modulator PM is a' three-electrode electron discharge device suit ably designed forrmodulating the carrier wave from the oscillator P0 in accordance with amplified picture current from the amplifier PQA. The demodulator RPD also 'mitted throng device. A relatively large grid polarizing battery 69 is used to accomplish demodulation. A condenser 70 is connect d between the cathode and anode of demodulator RPD to improve its operation.

Fig. 3 illustrates one arrangement for moving the drum 5 of Fig. 1 in an axial direction atthe same time that it is being rotated. The drum is carried on a shaft '75 which is'supported upon a'carriage76. The carriage 76is slidably mounted on frame 77, which carries-shaft 80.- Shaft 80 is secured to the upper friction member of clutch 8 and is rotated by phonic wheel 6. The rotation of shaft '80 causes the rotation of shaft and drum 5 through gear wheels 78 and 79. Gear wheel 78, while movable-along the shaft 80, rotates therewith by a key Wl'llCll slidable in a key way in shaft 80. The screw engagement of shaft with the threaded collar 81, which collar is secured to frame 6, causeframe 76 to slide on support 77 as shaft 80 rotates.

M ethod of operation.

The method of operation will now be described. 'The drums 5 and 12 are set at the starting position ,in any s itable manner.

in their starting position, due to the deenergizatibn of relays 45 and 47.1 The circuits of the electron dischaa'ge devices are then energized and phonic wheels 6 and 18 set in, rotation and allowed to at taln-synchronism under the control of the synchronizlng apparatus operate-d over the lower composite le of the composite sets 14 and. 15. The picture carrier wave sup.- plied by oscillator PO is impressed upon the modulator PM. This carrier f wave modulated by a constant amplitude current from the pict re amplifier PCA is trans amplifier SMA to demodulator RPD over transmission line L and reproducing amplifier RA. Demodulated cur;

rent flows in the movable strings of light valve 60.

Everything is in readiness to start the transmission of the picture. Phonic wheels 6 and 18 are rotated synchronously. Drums 5 and 17 are locked against rotation. Light valve 60 is energ'ized by demodulated current from the carrier wave.

To start the actual transmission, switch 419 is closed and kept closed during the transmission process. The varying tone values of the transparency of the picture cause varying currents through the photoelectric cell 50 as the drum 5 rotates and simultaneously moves in an axial direction-at a uniform rate. The 03.11161" wave from oscillator PO is modulated by these varying currents and after amplification in amplifier SNA is transmitted to the demodulator RFD. Corresponding varying currents in the output circuit of demodulator RPD cause the movement of the strings of light valve ('50 so that the light impressed upon the record blank is varied in accordance with the light transmitted through the transparency or the pic ture at the sending drum 5.

At the conclusion or the transmitting process the switch 49 is opened, thereby locking the drums 5 and 17 against further rotation. The drums may then be rotated to their starting position in any suitable manner, such as by reversing the motors in preparation for the transmission of another picture.

Various modifications of the specific embodiment of the invention which has been described can be made without departing from the scope of the invention, as defined in the appended claim.

W hat is claimed is:

in a picture transmission system, a rotatable sending member for mounting the picture to be sent, a source of picture current, a source of light, a photoelectric cell acted upon by said light and varying the intensity of the picture current in accordance with the lights and shades of said picture, means for generating a sustained oscillatory carrier current, a modulator for modulating the carrier wave in accordance with the amplitude of the picture current, a composite transmission line for transmitting the modulated carrier wave, a rotatable receiving member for mounting a sensitized element, a light valve responsive to the modulated carrier wave for I determining the amount or light reaching said sensitized element, rotary distributors, one at the sending end and one at the receiving end, a circuit including one component of said composite transmission line for sending currents from the sending "distributor to the receiving distributor, and means controlled by the receiving distributor for maintaining said rotatable sending and receiving members in syn-- chronisrni lln witness whereof, Y. hereunto subscribe my name this 13th day of May A. ll, 1924.

HARQLD ARNOLD: 

